1. Field of the Invention
Embodiments of the present invention generally relate to insertion techniques for watermarks. More particularly, the present invention relates to insertion techniques for low frequency watermarks.
2. Description of the Related Art
Watermarking is a technique that can be used to detect the origin of a copy of audio and/or visual media. This technique is especially beneficial in the motion picture industry. Typically, when a motion picture is released, there is a very large market for unauthorized copies of the motion picture. Watermarking facilitates the detection of the origin of any unauthorized copies. Watermarking information is very critical in eliminating, or at least minimizing, piracy of copyrighted audio/visual content.
Given these potential leaks, a content owner needs forensic tools that enable the tracking of unauthorized copies back to the party who licensed the use of the content, and who was responsible for preventing its further distribution. The ability of the content owners to identify the exact distribution point at which material was stolen can be used as a tool to identify the responsible parties and can act as a deterrent to such theft. A watermark uniquely identifying the licensee of that copy of the content can serve this purpose. This tracking watermark will give content owners a powerful forensic tool against piracy, because it allows them to trace pirated copies to the individual customers (e.g., for video download), or to a specific post-production house, or to the time and location (e.g., for digital cinema) at which theft occurred.
Most watermarking methods use high frequency techniques to insert watermarks into audio/visual content. However, there are problems associated with high frequency watermarking techniques. High frequencies should be avoided because the reduced sensitivity of the Human Visual System (HVS) at high frequencies allows these components to be distorted by processing or attacked by adversaries without significant degradation to the fidelity of the content. Thus, watermark data in these components can be damaged. One might conclude that since there is also reduced HVS sensitivity at low frequencies that low frequencies should be avoided for the same reason. However, the high degree of information in the low frequency components makes them difficult to distort without degrading the fidelity of the content. Most optical and computational processes that are applied to moving imagery and result in “matchable” quality tend to reproduce these low frequency/high information components with high fidelity. For example, camcorder piracy, which often degrades middle and high frequencies to the extent that typical spread-spectrum watermarks are significantly damaged, still generally produces a video stream from which a viewer could describe in detail what is happening in each scene.
Therefore, there is a need in the art for a method and apparatus to provide low frequency watermarking of content.